Forum Discussion
Fabric User Data Function parameter defaults?
Hi MangoMagic
Thank you for contacting the Microsoft Fabric Community Forum.
Currently, Microsoft Fabric's Python User Defined Functions (UDFs) created with the @udf.function decorator do not allow default values or optional parameters in their definitions. If you try to set a default value for a parameter, such as option: str = "Get watermark", the function will not publish or compile correctly in the Fabric environment.
To avoid issues, make sure all parameters are explicitly defined and provided when calling the function. If you need default behavior, handle it inside the function by checking if a parameter is empty or null and then assigning a value as needed. This method works within the platform's current limitations and ensures your UDFs will run as expected.
from microsoft.fabric import udf import microsoft.fabric.functions as fn @udf.connection(argName="sqlDB", alias="Control") @udf.function() def GetWatermark(sqlDB: fn.FabricSqlConnection, ID: int, option: str, description: str) -> list: if not option: option = "get watermark" else: option = option.lower() if option == "get watermark": query = f"EXEC [dbo].[Get_ETLSettings] @ID = {ID}, @Option = '{option}';" else: query = f"EXEC [dbo].[Get_ETLSettings] @ID = {ID}, @Option = '{option}';" connection = sqlDB.connect() cursor = connection.cursor() cursor.execute(query) results = cursor.fetchall() cursor.close() connection.close() return resultsRegards,
Karpurapu D,
Microsoft Fabric Community Support Team.
Community SupportHi MangoMagic
Thank you for contacting the Microsoft Fabric Community Forum.
Currently, Microsoft Fabric's Python User Defined Functions (UDFs) created with the @udf.function decorator do not allow default values or optional parameters in their definitions. If you try to set a default value for a parameter, such as option: str = "Get watermark", the function will not publish or compile correctly in the Fabric environment.
To avoid issues, make sure all parameters are explicitly defined and provided when calling the function. If you need default behavior, handle it inside the function by checking if a parameter is empty or null and then assigning a value as needed. This method works within the platform's current limitations and ensures your UDFs will run as expected.
from microsoft.fabric import udf
import microsoft.fabric.functions as fn
@udf.connection(argName="sqlDB", alias="Control")
@udf.function()
def GetWatermark(sqlDB: fn.FabricSqlConnection, ID: int, option: str, description: str) -> list:
if not option:
option = "get watermark"
else:
option = option.lower()
if option == "get watermark":
query = f"EXEC [dbo].[Get_ETLSettings] @ID = {ID}, @Option = '{option}';"
else:
query = f"EXEC [dbo].[Get_ETLSettings] @ID = {ID}, @Option = '{option}';"
connection = sqlDB.connect()
cursor = connection.cursor()
cursor.execute(query)
results = cursor.fetchall()
cursor.close()
connection.close()
return results
Regards,
Karpurapu D,
Microsoft Fabric Community Support Team.
Thank you, that worked 😃
Hi v-karpurapud I have a similar problem. In my use case, I am using UDF into powerbi report and passing the parameters through Text slicer. If I dont pass the value from pbi report, it doesn't enabled the button hence, I need to pass the all values irrespective it is required or not. Is there a workaround for same?
- v-karpurapud
Hi Sharmilshah
In Microsoft Fabric, Fabric UDFs require all parameters to be explicitly provided, and the Invoke Function visual in Power BI disables the button whenever any parameter evaluates to BLANK(). Because of this behavior, optional parameters or default values in the UDF signature are currently not supported.
To work around this, keep all parameters mandatory in the UDF signature and implement any “optional/default” logic inside the function by checking whether a parameter is empty or null and assigning a default value as needed. On the Power BI side, ensure that measures mapped to UDF parameters never return BLANK(). This can be achieved using SELECTEDVALUE() with a fallback value or COALESCE() for numeric parameters. For example, return "Get watermark" when no option is selected and "" for optional text fields instead of BLANK().Regards,
Microsoft Fabric Community Support Team.
